Among vitamins that are important for proper nutrition are fat-soluble vitamins, a group that includes vitamins A, D, E, and K. A vitamin may include any of a number of related compounds that may share structural and/or functional characteristics. For example, vitamin A includes a number of related and biologically active compounds such as retinol, retinoic acid, and retinal. Each of the aforementioned vitamin A compounds includes an unsaturated hydrocarbon-containing chain, and the compounds serve various roles in the body. For example, vitamin A compounds may be antioxidants and may decrease cellular damage that may otherwise occur from the presence of some reactive species that may be produced during metabolism.
In addition to chemical forms active in the body, a number of provitamin forms of vitamin A and other fat-soluble vitamins may be included in foods and beverages. Beta-carotene, for example, is a provitamin form of vitamin A that may be converted by enzymatic processes to retinol in the liver. Therefore, beta carotene may be an effective source of retinol if consumed, and beta carotene may be substituted for vitamin A in food and beverage formulations.
As well as serving as a source of vitamin A, beta-carotene may function as a pigment and strongly absorbs light in blue-green regions of the visible spectrum, a property that may be used to impart a deep reddish-orange or yellow coloration to food and beverage products. While beta-carotene possesses some desirable color properties, beta-carotene is not entirely stabile, and degradation of beta-carotene, which may be driven by either or both of heat and light, may limit the color stability of products incorporating beta-carotene. The limited photostability of beta-carotene, a characteristic shared by some other fat-soluble vitamins, may be associated with functional roles that make fat-soluble vitamins useful in the body. For example, the fat-soluble vitamins include species that may protect lipids from breakdown during metabolism; therefore, the ability of vitamins to interact with and potentially deactivate high energy intermediates, such as radicals and/or singlet oxygen, which may form from lipids or be present during lipid metabolism, may be a useful property. However, the capability of vitamins to interact with those intermediates may also facilitate undesirable reactions, such as oxidative decomposition, that may limit vitamin stability.
The aforementioned characteristics of vitamins and fats may pose challenges when incorporating fat-soluble vitamins in food and beverage formulations. For example, when used in those compositions, beta-carotene and/or other fat-soluble vitamins may be dispersed throughout the composition as an emulsion. However, when a vitamin is incorporated in the oil phase of an emulsion, a vitamin may be exposed to an environment that includes a surrounding concentration of lipids or fats, species that, as noted above, may break down to intermediate compounds that are capable of interacting with vitamins. In addition, in some consumable items, such as when a vitamin component is used to impart color to a food or beverage product, a vitamin may also be exposed to light which may further subject vitamin formulations to photochemical processes that may promote vitamin degradation. Therefore, use of fat-soluble vitamins in food and beverage formulations may commonly expose the vitamins to a number of conditions that limit their stability. There is a need for emulsions and consumable products including emulsions that impart color stability and/or minimize loss of vitamin activity in consumable compositions.